Fan comprising a cooling body consisting of heat-conductive plastic

ABSTRACT

The invention relates to a fan (1) comprising an electronic system on a printed circuit board (2) and a cover (10) arranged above the electronic system, which is embodied both as an active cooling body and a passive cooling body, wherein the cover (10) is designed substantially as a flat covering element consisting of a thin-walled plastic and has a form with a surface (11) which is effective for the cooling of the electronic system arranged beneath the cover (10), said surface being larger than the projected base area of the cover (10) by a factor of at least 2.

The invention relates to a fan comprising a cooling body embodied as aplastic cover.

A cooling body has the task of absorbing heat from an element to becooled and releasing it again to a surrounding medium. As such, amaterial of high thermal conductivity, such as aluminum or copper, istypically used for the cooling body.

Mass production of aluminum cooling bodies, in particular those whoseform is adapted to a predetermined application, is typically done usingthe die casting process. For this purpose, heated aluminum in the liquidor sticky state is pressed, under high pressure, into a preheated steelmold which will later serve as a conductive cooling body.

Cooling bodies are also used for motors. For example, DE 19841583 A1addresses a cooling body for cooling elements, in particularsemiconductor components, motors and aggregates, in particular a coolingunit at least partially made of extruded aluminum or other light metal,consisting of at least two separate base profiles for mounting theelectric components which are spaced apart from each other andinterconnected by means of a plurality of separate cooling fins.Further, the assembly of at least one fan is provided between twoadjacent base profiles.

It is convenient to utilize heat conduction for cooling. In physics,heat conduction—also known as heat diffusion or thermal conduction—isunderstood to mean the flow of heat induced by a difference intemperature. As such, according to the second law of thermodynamics,heat always only flows in the direction of the lower temperature, i.e.,in the direction of the temperature sink. Heat conduction is a mechanismfor transferring thermal energy without requiring a macroscopic flow ofmaterial as with the alternative mechanism of convection. Heat transferthrough heat radiation is also considered as a separate mechanism. Ameasure of heat conduction in a particular substance is thermalconductivity.

It is therefore obvious that, for utilizing cooling by means of acooling body, a substance or material of good to very good thermalconductivity is used. Copper and its alloys typically have thermalconductivity values of 100-400 W/mK: with 236 W/mK, aluminum is alsowithin a range of high thermal conductivity. As a metal material, evenunalloyed steel already has a significantly poorer heat conductionproperty and exhibits a thermal conductivity in the range of about 50W/mK.

Industrial plastics, such as PUR or polyimide (PA), are known in the artto be unsuitable as heat conductors due to their significantly lowerconductivity of not even 1/1000 of the value of copper. Thus, copperprovides a conductivity which is better than that of conventionalplastics by more than 1000 times.

In the case of fans and fan motors with an integrated electronic system,the electronic system naturally becomes warm or hot and must thereforebe cooled to avoid damage to the electronic system and increase itslifetime. While typical metallic covers dissipate heat well, they areexpensive to manufacture and not achievable in a cost-effective mannerdue to the high material price alone.

The object of the invention is therefore to provide cooling for theelectronic system of a fan motor of a fan, which can be producedcost-effectively and works reliably.

This object is achieved by the combination of features according toclaim 1.

A basic idea of the present invention is to cool the electronic systemof a fan using a plastic cooling body instead of a metal cooling body.This approach, which is unknown in the prior art, can be realized byusing the cooling body as a cover with a very thin wall thickness havinga specific form and surface.

In addition to increasing the surface area, several effects are used ina targeted and cumulative manner, namely heat conduction, heatconvection and the reduction of heat build-up, by using a thin-walledplastic material having a large efficient surface and a comparativelylarge proportion with a direct contact surface for heat-producingcomponents.

In this way, in a departure from the prior art, a cover enabling theresulting heat to be thermally dissipated can also be obtained with aplastic material in a cheap and efficient manner.

According to the invention, for this purpose, a fan is provided,comprising an electronic system on a printed circuit board, wherein,above the electronic system, a cover is provided which works both as anactive cooling body and a passive cooling body, wherein, for thispurpose, the cover is designed substantially as a flat covering elementconsisting of a thin-walled plastic and has a form with a surfaceeffective for the cooling of the electronic system arranged beneath thecover, said surface being larger than the projected base area of thecover by a factor of at least 2.

For this purpose, it is particularly advantageous if the cover has acooling fin structure with a plurality of cooling fins which increasethe effective surface.

It is further advantageous if the cover forms a plurality of recesses inwhich fastening holes are provided at which the cover is detachablyfastened to the fan by releasable fastening means.

It is further advantageously provided that the cover has, in the area ofthe cooling fin structure, a flat contact side for directly contactingheat-producing components.

In a further advantageous embodiment of the invention it is providedthat the cover has the cooling fin structure in one or more areas orforms a plurality of areas with such a cooling fin structure.

Furthermore, it is advantageous if the cooling fins are attached orformed to extend radially outwards, thereby implementing a structureopen radially outwards and upwards which has an advantageous effect onproduction and the cooling effect.

A further improvement can be achieved in that the cooling fins have achanging, in particular outwardly decreasing, wall thickness. Otherforms and configurations of the wall thickness are also conceivable toimprove heat dissipation effects. In principle, contrary to the metalbodies with large wall thicknesses usually used in the prior art,according to the concept of the present invention, an overall smallerwall thickness is aimed for in order to achieve rapid heat dissipationand also to prevent heat build-up.

A further optimization is a solution in which the cover forms a flatcontact surface on the bottom facing the electronic system and in which,in the assembled state, this contact surface at least partially abutselectronic components.

In an advantageous embodiment of the invention for a radial fan, thecover is formed from a substantially round section integrally joined toa projection (preferably with a linearly extending lateral edge).

It has also been shown to be advantageous if the material of the coveris a polyimide (PA), polyurethane (PUR), polycarbonate (PC) orpolyethylene (PE).

In a further advantageous embodiment, it is provided that the thicknessof the cover is smaller in the area parallel to the arrangement of theprinted circuit board and/or the area of the flat contact surface thanin a periphery or in the area of the cover extending towards theelectronic system by a factor of at least 2. As a result, the essentialstabilizing properties can be placed in the periphery and the essentialthermal properties in the flat area and the areas with the cooling fins.

Other advantageous developments of the invention are characterized inthe sub-claims or are shown in more detail below together with thedescription of the preferred embodiment of the invention with referenceto the figures.

Therein:

FIG. 1 shows a schematic sectional view through a radial fan,

FIG. 2 shows a perspective view of the radial fan of FIG. 1,

FIG. 3 shows a top view of the cover of the electronic system of theradial fan of FIG. 1,

FIG. 4 shows a perspective view of the cover of FIG. 3,

FIG. 5 shows a sectional view of the cover of FIG. 3.

In the following, the invention will be explained in greater detail onthe basis of an exemplary embodiment with reference to FIGS. 1 to 5, inwhich the same reference numerals indicate the same structural and/orfunctional features.

FIG. 1 shows a schematic sectional view through a fan 1, here a radialfan.

Fan 1 is embodied with an electronic system on a printed circuit board2. Above the electronic system, a cover 10 according to the invention isshown which is embodied both as an active cooling body and a passivecooling body. As such, as can be seen in FIGS. 3 to 5, cover 10 isdesigned as a substantially flat covering element consisting of athin-walled plastic and has a form with a surface 11 which is effectivefor the cooling of the electronic system arranged beneath cover 10, saidsurface being larger than the projected base area of cover 10 by afactor of at least 2 due to the cooling fin structure with a pluralityof cooling fins 12 as can be seen in FIG. 2. As can also be seen, thecooling fins run or extend radially outwards.

The projected base area can be seen in the top view from theillustration in FIG. 3. As can also be seen in FIG. 5, the effectiveactive surface is significantly increased by the fin structure. Cover 10is formed from a substantially central round section 17 integrallyjoined to a projection 18 with a straight lateral edge.

In FIGS. 3 and 4, it can be seen that cover 10 forms a plurality ofrecesses 13 in which fastening holes 14 are provided.

Operatively connected to the electronic system, cover 20 is detachablyfastened to fan 1 by releasable fastening means 15 (e.g., screws). Onthe bottom facing the electronic system, cover 10 forms a flat contactsurface 19 by which it at least partially abuts electronic components inthe assembled state.

In the sectional view through cover 10, as shown in FIG. 5, it has aflat contact side 16 for contacting heat-producing components of theelectronic system in the area of the cooling fin structure. It can alsobe seen that cooling fins 12 have a changing wall thickness, inparticular slightly decreasing from bottom to top, and taper slightly,so to speak.

The practice of the invention is not limited to the preferred exemplaryembodiments specified above. Rather, it is conceivable, to adapt theform and configuration of the cover correspondingly to the respectiverequirement and, for example, the number of areas with fin structures tothe specific cooling task.

1. A fan (1), comprising an electronic system on a printed circuit board(2) and a cover (10) arranged above the electronic system, which isembodied both as an active cooling body and a passive cooling body,wherein the cover (10) is designed substantially as a flat coveringelement consisting of a thin-walled plastic and has a form with asurface (11) which is effective for the cooling of the electronic systemarranged beneath the cover (10), said surface being larger than theprojected base area of the cover (10) by a factor of at least
 2. The fan(1) according to claim 1, characterized in that the cover (10) has acooling fin structure with a plurality of cooling fins (12).
 3. The fan(1) according to claim 1, characterized in that the cover (10) forms aplurality of recesses (13) in which fastening holes (14) are provided atwhich the cover (20) is detachably fastened to the fan (1) by releasablefastening means (15).
 4. The fan (1) according to claim 2, characterizedin that the cover (10), in the area of the cooling fin structure, has aflat contact side (16) for contacting heat-producing components.
 5. Thefan (1) according to claim 2, characterized in that the cover (10) hasthe cooling fin structure in one or more areas.
 6. The fan (1) accordingto claim 2, characterized in that the cooling fins (12) are attached orformed to extend radially outwards.
 7. The fan (1) according to claim 2,characterized in that the cooling fins (12) have a changing, inparticular outwardly decreasing, wall thickness.
 8. The fan (1)according to claim 1, characterized in that the cover (10) forms a flatcontact surface (19) on the bottom facing the electronic system, and inthat, in the assembled state, this contact surface at least partiallyabuts electronic components.
 9. The fan (1) according to claim 1,characterized in that the cover (10) is formed from a substantiallyround section (17) integrally joined to a projection (18).
 10. The fan(1) according to claim 1, characterized in that the material of thecover (10) is a polyamide (PA), polyurethane (PUR), polycarbonate (PC)or polyethylene (PE).
 11. The fan (1) according to claim 8,characterized in that the thickness of the cover (10) is smaller in thearea parallel to the arrangement of the printed circuit board (2) and/orthe area of the flat contact surface (19) than in a periphery (20) or inthe area of the cover (10) extending towards the electronic system by afactor of at least
 2. 12. The fan (1) according to claim 1,characterized in that the fan is a radial fan.